A menstrual “period” is the result of normal hormonal changes that tell the ovaries to ovulate or produce an egg. Menstrual periods are normal to have and they normally occur every 21 to 35 days in premenopausal women.
They are triggered by a fall in progesterone levels in the blood which causes the endometrium (uterine lining) to shed. This shedding produces uterine/vaginal bleeding that normally lasts no more than 7 days.
However, there are other types of uterine bleeding that may be misinterpreted as a menstrual period. The most frequent reason for abnormal uterine/vaginal bleeding that is not a true menstrual bleeding is bleeding due to breakdown of the uterine lining from lack of the proper hormone levels (often called anovulatory or dysfunctional uterine bleeding).
This can occur at any age between the onset of menstruation and menopause (the “change”) but most frequently occurs in the years just prior to menopause and during the teenage years.
It is the result of the brain not telling the ovaries to ovulate. Therefore ovulation does not occur and the endometrium does not receive the ovarian hormones it needs to grow and develop. As a result, it breaks down or sheds, erratically over weeks and may cause bleeding for weeks or even months.
Other less common reasons for uterine/vaginal bleeding include breakthrough bleeding while on hormones such as the oral contraceptive pill (“the pill”), and bleeding from a precancerous or cancerous lesion, endometrial polyps, or uterine infection.
All of these types of uterine/vaginal bleeding occur regardless of whether uterine fibroids are present.
Uterine fibroids cause whatever uterine bleeding that occurs to be heavier, longer, or both. It causes normal menstrual bleeding to become heavier and/or longer, and can also make other types of uterine bleeding heavier and/or longer. Fibroids do not usually cause bleeding to occur. Rarely, uterine fibroids growing on a stalk within the uterine cavity can cause bleeding once they become large.
The excessive bleeding due to fibroids may be treated by destroying or removing the fibroids or by minimizing the development of the uterine lining (endometrium) with hormones (typically the oral contraceptive pill or progestin therapy). However, hormone therapy will not reduce the pressure symptoms that fibroids also cause as they enlarge (urinary frequency, pelvic/abdominal pressure, abdominal distension, backache).
Fibroids may also grow during hormonal therapy (please see the section Estrogen and Fibroids – You Will Be Surprised). Treatment with progestin agents such as progesterone creme or norethindrone for more than a brief time will likely increase fibroid growth.